The answer is surprisingly complex and contested. While the meteorological phenomenon is real—a period of unseasonably warm, dry weather occurring after a killing frost—the origin of its name is a tangled weave of history, culture, and folklore, with no single definitive source.
It is a time for “second springs,” where dormant plants may briefly bud again. This specific, predictable pattern is key—the term is not used for just any warm day in autumn. origin of indian summer